Feral cats are more abundant under severe disturbance regimes in an Australian tropical savanna

Date: 20, Apr, 2020
Author(s):   Davies H.F., Maier S.W., Murphy B.P.
Publisher: Wildlife Research

Context: There is an increasing awareness that feral cats play a key role in driving the ongoing decline of small mammals across northern Australia; yet, the factors that control the distribution, abundance and behaviour of feral cats are poorly understood. These key knowledge gaps make it near-impossible for managers to mitigate the impacts of cats on small mammals.

Aims: We investigated the environmental correlates of feral cat activity and abundance across the savanna woodlands of Melville Island, the larger of the two main Tiwi Islands, northern Australia.

Methods: We conducted camera-trap surveys at 88 sites, and related cat activity and abundance to a range of biophysical variables, either measured in the field or derived from remotely sensed data.

Key results: We found that feral cat activity and abundance tended to be highest in areas characterised by severe disturbance regimes, namely high frequencies of severe fires and high feral herbivore activity.

Conclusions: Our results have contributed to the growing body of research demonstrating that in northern Australian savanna landscapes, disturbance regimes characterised by frequent high-severity fires and grazing by feral herbivores may benefit feral cats. This is most likely to be a result of high-severity fire and grazing removing understorey biomass, which increases the time that the habitat remains in an open state in which cats can hunt more efficiently. This is due to both the frequent and extensive removal, and longer-term thinning of ground layer vegetation by severe fires, as well as the suppressed post-fire recovery of ground layer vegetation due to grazing by feral herbivores.

Implications: Management that reduces the frequency of severe fires and the density of feral herbivores could disadvantage feral cat populations on Melville Island. A firm understanding of how threatening processes interact, and how they vary across landscapes with different environmental conditions, is critical for ensuring management success.